In the course of manufacturing an integrated circuit, it becomes necessary to planarize the surface. For example, as shown in FIG. 1, a line of metal 14 has been etched from a continuous layer and sits atop substrate 11, with intermediate glue layer 13. Prior to application of the photoresist used to define the shape of line 14, an anti-reflection coating (ARC) 15 of titanium nitride was applied to the metal surface. After etching, the titanium nitride remained in place. This was followed by the deposition of a conformal layer 12 of oxide for the purpose of keeping the SOG from touching the metal. In order to planarize the surface, a layer of spin on glass (SOG) 16 was then applied.
To guarantee that all projections are covered, layer 16 is necessarily too thick and must be etched back until the highest projection is just exposed. In this example, this would be the top surface of titanium nitride layer 15, giving the structure the appearance shown in FIG. 2 where layer 26 represents the original SOG layer 16 after etchback. It has been found that as a byproduct of this etchback process a polymeric residue is formed. The exact composition of this residue is not known but it has been found to include both titanium and fluorine. This residue is most commonly seen in the form of particulate contamination such as particle 22.
Traditional methods for removing this source of contamination, such as the application of RF (radio frequency), have proven to be unsuccessful. The present invention provides a simple, but effective, method for preventing the formation of the polymeric residue.
In the course of searching for prior art, no invention teaching the precise method of the present invention was found. Several references were, however, found to be of interest. For example, in U.S. Pat. No. 5,472,825, Sayka shows an argon plasma treatment of a SOG layer after an etchback to densify the SOG layer. In U.S. Pat. No. 5,679,211, Huang shows a method of etching back SOG using an oxygen-containing gas plasma treatment (e.g. Ar/0.sub.2) that removes SOG residues. In U.S. Pat. No. 5,639,345, Huang et al. show a method for a two step etch back of an oxide and SOG layer, while in U.S. Pat. No. 5,631,197 Yu et al. also show a SOG etch back process.